Insulating structure for high-potential condenser terminals and the like



No'v. 29, 1927.

w. DUBILIER I INSULATING STRUCTURE FOR HIGH POTENTIAL CONDENSER TERMINALS AND THE LIKE Filed Feb. 18. 1921 INVENTOR ldg lgr M "URI/E78 'Patented Nov. 29, 1927.-

WILLIAM DUIBILIER, OF NEW YORK, N. 'Y.,

1,650,983 PATENT OFFICE.

ASSIGNOR 'lO DUIBILIER CONDENSER COR- 'IPOBATION, A. CORPORATION OF DELAWARE.

INSULATING STRUCTURE FOR HIGH-POTENTIAL CONDENSER TERMINALS AND THE Application med February is, 1921. Serial No. 445,948.

The invention has for an object to'provide an insulating sup orting' structure for conductors used with igh potential, high frequency circuits, of such character as to be capable of withstanding long continued use under very severe electrical conditions, without substantial losses or undue heating or deterioration due to other causes such as puncture creepage, and brush discharge or corona e ects,

Another object is to provide a. structure wherein the above-mentioned features are combined with sufficient mechanical strength and elasticity to insure that mechanical injuries will be. minimized and obviated, such as might arise, for example, from shocks or temperature changes.

The invention also embodies an insulating structure of the above character having a small capacity, and low phase angle or phase difierence, in order to reduce to safe limits the energy lossesoccurring therein.

A further object of the invention is to rovide a structure to be utilized with a igh frequency electrical condenser, and particularly the high tension terminal thereof, for the purpose of enabling the condenser and terminal to operate to the best advantage, when high frequencies and undamped or continuous wave lengths are emplo ed. 1

- her objects and advantages of the in- 'vention will be in art obvious and in part specifically pointed? out in the description hereinafter contained which, taken in connection with the accompanying drawings,

discloses a preferred embodiment of the indill vention; such embodiment, however, is to be considered merely as illustrative of its principle. In the drawin 2 Fig. l is a side view 0 a high potential condenser container equipped with a terminal structure made in accordance with the invention for the purpose of leading a high potential terminal through the cover of the container. Certain parts are broken away more clearly to show the details of the said structure; and i Fig. 2 is a plan view of the structure shown in Fig. 1.

When condensers are used with radio transmitting sets of the vacuum tube type for example, and the apparatus is subjected to undamped high frequency oscillations such severe strains are set up upon the terminal insulation of the condenser that'if ordinary means for insulating the terminal be employed, the insulating medium rapidly deteriorates and breaks down due to the effects of the field which exists between the terminal and surrounding metal parts, and other causes.

Many other instances also will occur to those skilled in the artin which the dilficulty is present of insulating a high tension conductor employed in high frequency and high potential apparatus under such circuit conditions, especially with continuous waves that ordinary insulations are either wholly ineiiectual or deteriorate rapidly, due to such causes as heating, brush discharge, or corona effects, with the result that the terminal insulation is very unsatisfactory. In the case of insulating materials heretofore used for such purposes, it is found that the insulation tends to deteriorate gradually under the electrical strains, and heats up, due

to the energy losses therein, the heating increasing as the material deteriorates, and

the phase angle or hase difi'erence and losses increasing rapidly upon increased temperature, with the result that a multi lication of losses and deterioration takes p ace with continued use. Furthermore, mechanical difliculties are encountered in the use of certain insulating materials, such as orcelain, which tends to break or crack uring use due to many causes, for example, shocks due to gunfire on board ship, temperature changes, etc.

According to the present invention, an insulating structure is used of such character as to reduce the energy losses and heat rise as far as possible, both by means of the insulating material employed and the construction of the insulator, and also to avoid deterioration or mechanical injury due to long continued use.

The forms of the invention illustrated, are disclosed as adapted and applied to a high potential condenser, comprising a condenser unit 1, enclosed in a metal container 2, which latter may constitute one terminal of the conthat the cover 3 is suitably attached to the body of the container as by means of the screws 4 shown in Fig. 2. a

As appears more particularly in Fig. 1 the wall through which the high otential conductor is to be led, is provide with a relatively large opening 5, across which is disposed a sheet mica diaphragm or plate 6, the latter being firmly seated against the walls of the opening, for example by means of a metal ring 7 underlying the edges of the diaphragm and secured in place by means of a plurality of screws 8. Preferably the edges of the metal parts around the diaphragm 6 are somewhat rounded in order to reduce the tendency toward arcing or brush discharge, and I also prefer to taper the walls of the cover 3 away from the condenser unit, as shown in Fig. 1, in order to provide a greater electrical spacing of the cover from the parts of the condenser unit which are at a 'difi'erent potential therefrom, and also to provide more space to accommodate the terminal structure without bringing the latter too close to the condenser unit.

The diaphragm or plate 0 is of such large extent as to provide a large crecpage distance between the walls of the cover 3 and the high tension conductor or terminal post, which will insure against the occurrence of corona along the surfaces of the laminations making'up the plate, under the conditions of use for which the condenser is designed. That is to say, there is a tendency for corona efiects to take place not only along the exterior surfaces of the plate 6, but also be tween the laminations thereof, so that the plate should be of relatively large diameter. For example, where the structure is to be used in connection with sustained undamped oscillations of very high frequency, say 100, 000 to 1,000,000 cycles, at about 10,000 volts, the active radius of the diaphragm or plate 6 should be about one inch or larger.

I also prefer to interpose between the plate 6 and the high tension conductor 9 a tube 10, consisting of wound sheet mica, the walls of the tube thus constituting a barrier between the conductor and the surrounding metal parts, which will prevent breakdown even though the relatively large extent of diaphragm 6 should prove insuiiicient at certain times. However, the thickness of the tube 10 is best made small relative to the diameter of the plate, so that the interposition of the tube between the plate and the conductor 9 does not result in undue concentra- On opposite sides of the diaphragm 6 there are dis )osod laminated mica locks 11, such blocks "eing of sufiicicnt thickness to rovide a relatively large electrical spacing etwcen the portions of the conductor 9 which are exposed beyond their. ends and the metallic walls of the cover 3. It will thus be seen that a creepage path from the cover 3 to the exposed portions of terminal 9 must necessarily include the surfaces 12 of the mica blocks 11, and such surfaces being composed of the edges of the mica sheets are particul'arl resistant to creepage. If desired, the surfaces 12 of blocks 11 may also be corrugated to lengthen the creepage distance, as shown in Fig. 1. In the form shown it will be noted that the creepage path is broken up into two distinct surfaces. That is to say, it includes not only the surfaces 12 of blocks 11, but also the sides or faces of the mica sheets making up the diaphragm 6, so that any discharge would have to bridge these two surfaces in series.

It will be noted that a terminal structure of the above character is homogeneous as regards the dielectric or insulating material employed. That is, there is novariation in the characteristics of the insulation such as would tend to concentrate the electrical stresses on the weaker portions of the structure. The insulator is composed entirely of mica, a dielectric material which will not deteriorate with continued use provided corona effects or brush discharge are overcome, and the energylosses within the in sulator structure are very small, for many reasons. One important factor in securing this result is the very small capacity of the insulator, due to its structure and the rela tion ofthe metal parts associated with it, for

loo

example. where the terminal structure is amount of energy taken up by the terminal insulator depends upon the ratio of its capacity to the capacity of the condenser unit proper.- Thus, by keeping the capacity of the-insulator as small as possible, energy losses and consequent heating of the insulation are avoided. Where a terminal structure of the above character is employed at 10,000 volts, its resultant capacity then need not be greater than a few micro-microfarads. The elimination of corona efi'ects also is important in obtainin a structure which will not heat unduly. Turthermore, the mica making up the insulator is'mechanically strong, will withstand shocks without injury, and is not liable to be cracked, by tem erature changes.

It is -preferahle that the mica blocks 11 and the diaphragm 6 shall be tightly clamped together to prevent internal loosening, as by means of suitable bearing means or members 13 and 14 disposed on t e outer incense ocks l1, suitable means being the bearing members tosuch as a nut 15, threaded on the end terminal post 9 making up the insulating structure, I "o subject'the mica layers thereof to ressure as possible to bind the strucineo solid mass, and make the spaces the laininations as small as practising compound, such as parafin, Kane, hfiontan, or a mixture of these Waxes, ievent as as possible subsequent abtion of moisture by the insulator, and "bstitute the insulating compound for o o c r or moisture which otherwise might remain becween the mica layers. The imor'egnating bath may also be supplemented vacuum, "which will assist in removing moisture from the structure, and he above steps are completed the in is preferably subjected to a high at least in the neighborhood of 1 souare inch, in order that as small The dia- 1 phragm 6, however, particularly as reinforced by the blocks 11, is comparativel rugged and not liable to injury in use. t will be understood that the inner end of the terminal 9 has a suitable connection (not shown) with the condenser unit.

While mica is preferred as the material for the diaphragm and blocks 11, any other kind of insulation which is tenaceous and not brittle or fragile, and resistant to heat, and has the other properties of mica insulation, is of course to be regarded as the full equivalent thereof.

While a specific embodiment of the invention has been described, it is obvious that many changes may be made therein Without departing from the spirit of the invention, as defined in the following claim.

I claim:

In an electrical condenser comprising a metal casing enclosin the condenser ele ments and connected t ereto to constitute a terminal thereof and having an opening for a second condenser terminal connected! to said condenser elements, the improvement in insulating such terminal from the casing and in supporting it independently of the condenser elements, which comprises an insulating plate mounted on such casing over such opening and centrally perforated to surround and surrounding such second terminal, means for supporting such terminal on said insulating p ate, and a clamping ring metallically secured to such metal casing around its opening and securing said insulating plate to the casing in position to close such casing opening. i

In testimony that I claim-the foregoing, l have hereunto set my hand this th day of February, 1921.

WILLIAM DUBILIER. 

